Currently, the scanning electron microscope (hereinafter, SEM) is widely used in observation of submicron- and nano-sized samples. The SEM is designed to form an image by irradiating a sample with primary electrons emitted from an electron source while scanning the primary electrons, and by detecting secondary electrons that are generated in the sample. Here, the secondary electrons can be grouped into “true” secondary electrons characterized by having an energy of 50 eV or less, and backscattered electrons having an energy nearly equal to the incident energy of the primary electron. It is possible to obtain the contrast that reflects the differences in the shape of the pattern surface, the potential, the work function, and the like from the “true” secondary electron. On the other hand, it is possible to obtain the contrast that reflects the difference in the pattern material from the backscattered electron (See Non-patent Literature 1).
Recently, SEMs developed by different companies have included a plurality of detectors, enabling users to obtain images with various contrasts. On the other hand, it is difficult to interpret the image contrast and there is an increased demand for a quantitative analysis of the energy of secondary electrons detected by the SEM. In addition, it is necessary to perform an energy analysis on the secondary electrons under the condition in which the energy of the primary electrons is low, in order to reduce the damage to the sample caused by primary electron irradiation. As a method for performing the energy dispersion of secondary electrons in SEM, for example there is known a method described in Patent Literature 1.